In medical radiology, 3D images of a body are reconstructed with the aid of a C-arm rotating around a patient. In such an arrangement, images of high-contrast objects such as e.g. contrast-agent-filled vessels and images of low-contrast objects such as tissue are generated and 3-D structures can be visualized morphologically for interventional purposes. The rotations of the C-arm around a patient generally last about 5 seconds to 20 seconds. In order to obtain functional information in addition to the morphological data, a faster rotation of the C-arm around the patient is necessary.
The movement of the C-arm around the patient entails the risk of a collision of the C-arm, in particular of the X-ray detector or of the collimator, with the patient, staff or other objects of equipment in the room. This is usually avoided in current practice by the physician's performing a slow rotation monitored by him/her—a test run—before the automatic rotation is initiated. In this case he/she monitors the run for potential collisions. The most critical area is, of course, the area of the patient, especially in the event of unexpected patient movements.
In order to avoid injury to the patient as a result of a collision with the C-arm, additional sensors are mounted on the X-ray detector and the collimator. If said sensors are activated, the movement of the C-arm is stopped. If the rotation times are shortened, i.e. the rotation speeds are increased, this protection is no longer sufficient.
Solutions for collision avoidance have already been proposed, e.g. image-based monitoring approaches or approaches using a special collision sensor system (e.g. the non-pre-published patent application DE 10 2007 003 876.5).